The present invention relates to a method and a device for operating an electrical supercharger, at least one component connected to the intake manifold of an internal combustion engine being diagnosed on the basis of the operation of the electrical supercharger.
Enhancing the performance of an internal combustion engine by compressing the air necessary for combustion of the fuel using an exhaust turbocharger, which includes a turbine and a compressor operated in the air supply to the internal combustion engine, is conventional. Supporting the exhaust turbocharger using an auxiliary electrical drive to improve the response behavior of the exhaust turbocharger is conventional. This may, for example, be achieved via an electric motor, integrated in the exhaust turbocharger, which drives the shaft of the exhaust turbocharger supportingly at low speeds of the internal combustion engine. For example, operating an electrically-operated charge air compressor, which is also referred to as an electrically operated auxiliary supercharger (EL), in series with a conventional exhaust turbocharger in the air supply of the internal combustion engine is described in U.S. Pat. No. 6,029,452.
A method for testing the reliability performance of a fuel tank venting system, in which, during operation of the internal combustion engine, the fuel tank venting valve is closed and the fuel tank shutoff valve is opened for monitoring purposes during supercharger operation is described in German Published Patent Application No. 43 12 720. The reliable performance of the fuel tank venting system is determined using the overpressure which builds up in the fuel tank.
Other methods for diagnosing a fuel tank venting system use additional pressure sources, with the aid of which tightness tests of the fuel tank venting system are performed (for example, German Published Patent Application No. 198 09 384).
By activating the electrically operated supercharger after the vehicle is stopped, a further operating range for the engine control system is opened, in which functions are performed which relate to an air flow in the intake manifold and/or in the exhaust system of the vehicle. The flexibility of an engine control system, e.g., in the diagnostic area, may be significantly enhanced in this manner.
The electrically operated supercharger may be activated after the engine is turned off to cool the engine using the air flow guided through the engine and/or to cool the catalytic converter(s) in the exhaust system, which are cooled down by the flow of fresh air generated by the electrically operated supercharger.
Advantages may result in the diagnostic area through the operation of the electrically operated supercharger after the engine is turned off. In this case, various components connected to the intake manifold and/or the exhaust system may be diagnosed when stopped, with the engine turned off. At the same time, diagnostic methods may also be used which may require a pressure or an air flow in the intake or exhaust system. Operation of the engine may therefore not be necessary, which saves computer time, memory space, etc.
In this manner, optimized diagnostic methods for components connected to the intake manifold and/or exhaust system are made possible.
A more exact diagnosis may be possible than using diagnosis during driving, since well-defined environmental conditions exist when the engine is turned off.
Furthermore, in some cases components may be dispensed with, for example, the overpressure pump for diagnosing the fuel tank venting system.
By operating the electric supercharger after the engine is turned off, diagnosis of the fuel tank venting system of an internal combustion engine may be made possible, e.g., leak detection in the fuel tank venting system, testing the function of the fuel tank venting valve and shutoff valve (tightness tests), diagnosis of exhaust recirculation and/or circulating air valves, tightness testing of throttle valve, idle speed control, and (in diesel engines) exhaust valve, diagnosis of air flow sensor and intake manifold pressure sensor, and/or diagnosis of the turbo blower, of lambda probes, and various temperature probes such as exhaust temperature sensor, intake temperature sensor, etc.
A well-defined valve overlap (intake/outlet valve) may be performed to improve the flow rate to the exhaust system by activating a crankshaft starter generator connected to the power train. This generator operates the internal combustion engine so that the settings of intake and outlet valves result in a well-defined valve overlap and therefore in opening a cross-section between the intake manifold system and the exhaust system.